Yannick Nézet-Séguin conducts the Philadelphia Orchestra Thursday night at Saratoga Performing Arts Center. Here are some photographs from the performance. Nézet-Séguin takes the stage again tonight to conduct Masterpieces Past and Present. The Philadelphia Orchestra will be performing at SPAC through Aug. 18. For complete program details or tickets, go to spac.org or call (518) 584-9330.